Inghouse electric



July 5, 1927. 1,634,390,

V.-K. ZWORYKI'N WIRELES$ TRANSMITTING SYSTEM Filed March 1924 5 Sheets-Sheet l g 1 F INVENTOR WiTNESSE S:

ATTORNEY July 5,1927. T I 1,6345390 v. K. ZWORYKIN WIRELESS TRANSMITTING SYSTEM F l d March 17, 1924 5 Sheets-Sheet g H II WITNESSES: INVENTOR V fid/m/M. Z Wary/rm July 5 1927.

v. K. ZWORYKIN WIRELESS TRANSMITTING SYSTEM Filed March 17, 1924 5 Sheets-Sheet 5 WITNESSES: INVENTOR I WM WMA ATTORNEY July 1 v. K. ZWORYKIN WIRELESS TRANSMITTING SYSTEM Filed March I7, 1924 5 Sheets-Sheet 4 WITNESSES:

INVENTQR ATTORNEY Patented July 5, 1927.

UNITED STATES PATENT OFFICE.

VLADIMIR K. ZWORYKIN, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WEST- SYLVANIA.

WIRELESS TRANSMITTING SYSTEM.

. lpp'lieation filed March 17, 1924. Serial No. 699,629. 2

' arrange the transmitting circuits in a system of the above-indicated character that.

the transmitting station radiates, in addition to the signalling frequency, a masking frequency that is inaudible at a prede- 1 termined receiving station or stations, but

which indiscriminately obliterates the speech frequency at stations that attempt to listen in on the signalling.

Still another object of my invention is to accomplish the above results in a relatively simple manner without the use of a large amount of apparatus.

The above and other objects of my invention will be described hereinafter with ref-' erence to the accompanying drawings.

Referring now to the drawings,

Figure l is a diagrammatic view of the circuits and apparatus at the transmitting station;

Fig. 2 is a diagrammatic View of the circuits and apparatus of the equipment located at a receiving station;

Figs. 3, 4, 5 and 6 are detail Views of p01- tions of the apparatus at the transmitting station; 1

Fig. 7 is a view of a modified form of transmitting equipment for securing the same results as theapparatusshown in Fig. 1, and

I Fig. 8.is a diagrammatic View of'the cir-. cuits and apparatus of a transmitting and receiving station whereby secret signalling is accomplished in a different manner than in the previous figures,

Fig. 9 is a diagrammatic view of the circuits and apparatus of a combined transmitting and receiving station in which certain portions of the apparatus are common to both the transmitting and receiving devices.

Essentially, my invention consists in a transmitting station, shown in Fig. 1, and a receiving station, Fig. 2. At the transmitting station; a synchronizing current of a predetermined frequency is generated, which serves to intermittently interrupt the radiation of the signalling current and causes, during such interruptions. a so-called masking current to 'be radiated. At the receiving station, both the signalling current and the masking current are received. as well as the synchronizing current. The synchronizing current controls the receiving device so that it serves only to detect the signalling current.

Referring now more particularly to Fig. 1, the oscillating circuit including the antenna 1 is connected through a transformer 2 to the output circuit of an amplifier triode 3. The grid circuit of the amplifier triode 3 is connected through a transformer 4 to the plate circuit of a modulator triode 5. The grid circuit of the modulator triode 5 is connected through a transformer 6 to a circuit that is adapted to generate an oscillating current and which includes an oscillator triode 7. The grid circuit of the modulator triode 5 is also connected to an amplifier triode 8. The grid circuit of the amplifier triode 8 is connected through the secondary winding of a transformer 9 to a metal plate 10 in a cathode-ray tube 11.

The cathode-ray tube 11 is similar to an ordinary cathode-ray oscillograph and has a hot cathode 12, a diaphragm 13 and a tubular anode 14 enclosed in an evacuated container 15, the opposite end of which is occupied by the plate 10. The primary Winding of the transformer 9 is connected in circuit with a microphone 16 of the usual type. A generator-20 that generates a current of predetermined frequency, which will be referred to as the operating frequency current, is also connected in the grid circuit of the modulator triode 5 and serves to modulate the oscillating current generated by the oscillatory circuit including the 0scillator triode 7, and this modulated highfrequency oscillating current is amplified by the amplifier triode 3 radiated by the antenna 1.

Another cathode-ray tube 21, having the usual hot cathode 22, diaphragm 23, tubularanode 24, evacuated container 25 and metal plate 26, also has its metal plate 26 connected in the grid circuit of amplifier triode 8 through the secondary winding of a transformer 27. The primary winding of this the negative, using the terms used ,respectively.. These coils are'so positioned transformer is connectedin circuit with a 1 generator 29, that generates a current having a'variableaudio, frequency. qThis generator may take any well known form in order to. produce a constantly quency.

The construction of themetal plates and 26 maybe seen in detail in Figs. Hand 4. It will be seen that the metal plate 10 has a number. of rectangular holes cut I therein and that the metal plate 26 also has a number of rectangular holes.

The holes in the plate 26ers so outwith respectto the holes in the plate 10 that the uncut por-' with respect to the cathodea'ay tubes 11 and 21 thattheir magnetic field lies in a plane that is perpendicular to the line of the holes across either of the plates 10 and 26. At the receiving station, Fig. 2 an oscillatory circuit, including an antenna 40, is"

connectedthrough a tuning coil 41 to the grid of an amplifier 'triode 42. The grid of I this amplifier triode 42is also connectedw through a transformer 43 to the grid of a detector triode 44. The transformer .43 is adapted to receive current of the particular frequency sent out by the high-frequency current generator from the circuit. The plate of the detector triode 44 is connected to plates 45 and 46 placed in a cathode-ray tube 47. The cathode-ray tube 47 is some what similar to the transmitting cathoderay tubes previousl described and has a. hot cathode 48, a dlaphragm 49, a tubular anode 50 and a plate 51, the whole being enclosed in an evacuated vessel 52. The plate 51 has a number of holes cut in it which are exact duplicates in both position and size of the holes cut in the plate 10. The plate of the amplifier triode 42 is connected through the primary winding of a transformer 53 to the plate 51 in the cathode ray tube 47. The secondary winding of this transformer is connected to the grid of the detector triode 54, the plate circuit of which is connected to the telephone receiving device which, as shown, may be any kind of a speech receiving or recording device.

The modification of the transmitting circuit shown in Fig. 7 comprises an oscillatory circuit including an antenna 60. This oscillatory circuit is connected through an aimplifier triode 61 and a modulator triode 62 to a circuit that is adapted to generate an oscillating current and which includes an oscillator triode 63. The grid circuit of the amplifier triode 62 is also connected in cirvarying audible frecuit with the an'q'ilifiertriode 64 through a transiormer (if). 'lhegrnl circuit of the am-v phher trlode 64 is connected through the secondary windingsof the transformers (35 and tit; to metal plates 67' andtih m u-cuthode-ray tube (59. The primary winding of the tral isformer (35 is connectedin circuit with a variable frequency generator 70 and the primary winding of the transformer (36 lS'CUHHQtiOtl in the circuit of a telephone transmitter 71.

The cathode-ray tubetii) issimilar to the same manner as before mentioned. ".lhat is, assuming thatpthe cathode beam traverses "one ispositi-ve undonev isnegative, in the'fi thesc'plates i-n 'thedirection in'which the" openings are cut. the cathode'beam will first encounter the metal plate 26, etc.

A generator 73 is a amplifiertriode '62, and, as heretofore ex-' 'plained, is adapted to generate an alternating current having a frequency above audi-' bility, for-example, ofsubstantially 25,000 cycles. Coils '74 and? 5 associated with the cathode-ray tube 69 are connected in circuit plate 67,.then the metal lso associated with the I no I with the generator 73.:1he coils 74 and 75 are. so positioned with respect to the openings inthe'plates 67 andGS that-the'mag- .netic' fields genera-ted by current traversing the same will lie at right angles to the line of the openings in either the plate 67 or the plate 68.

The plate shown in Fig. 6 illustrates a manner in which non-uniform holes may be cut in plates, such as 10. 26, 67 or 68, so as to secure still further masking of the message or signal to be transmitted. The plate that is adapted to operate in connection with the plate shown in Fig. 6 will be a positive of the one shown.

In Fig. 5 is shown a plate' marked into divisions. thirty-two in number, which may be used for a coding plate in a manner tha will be described hereinafter.

In Fig. 8, an oscillatory circuit, including an antenna 80, is adapted to oscillate at two distinct frequencies. This circuit is connected through a transformer 81 to an amplifier triode 82. The grid circuit of the amplifier triode 82 is connected through a transformer 83 to a modulator triodc. 84.

The grid circuit of the modulator triodo 8t 2 that generates a current of operating frequency. The generator 87 that generates the operating frequency current is also connected to an oscillogi'aph element 89. The ().\".'lllt) "l'll)ll element 89 may he of any ordinary type. and ts mirror is adapted to scan the lcir= an and to divert the rays .coniing therefrom upon photoelectric cells J1 and 92.

Considering the lLllri fit). this lens is made up of two distinct light transmitting sections 1) and 94-. The section 93 is broken up non-unifornily hy opaque markings. The section 1H is also broken up, at varying (listances, with opaque markings. these distances being so determined that the section 93 may inc-considered positive and the section 94 may he considered negative.

By reason of the difference in position hetween the sections 93 and 94., the angle at which the light strikes the oscillograph mirror is different in the one case than in the other and, consequently, the light rays from the section 93 are deflected on the photoelectric cell 92, while the light rays from the section 94 are deflected on the photoelectric cell 91.

The photoelectric cell 91 is so positioned with respect to the oscillograph 89 that the light rays reflected from the various parts of the section 94 will always fall upon the photoelectric cell 91. This is accomplished by so placing the photoelectric cell that the an- "1c of turning of the oscillograph element 89 from one light transmitting section to the next is equal to the angle of its turning with respect to the photoelectric cell 91. The photoelectric cell 92 is similarly positioned to receive the light from the parts of the section 93.

The photoelectric cell 91 is connected through a transformer 92' to an amplifier triode 93. The amplifier triode 93' is connected to the grid of a. modulator triode 94. The photoelectric cell 91 is also connected through a transformer 95 to generator 96 that is adapted to generate current of a variable audio frequency. The grid of the ,ll'lOtllllfltOI' triode 94' is also connected to a circuit that is adapted to generate an oscillating current and which includes an oscillator triode 97, through a transformer 98. The output circuit of the modulator 94' is connected through a transformer 99 to an amplifier triode 100. The output circuit of the amplifier triode 100 is connected through a transformer 101 to the antenna 80. The )hotoelectric cell 92 is connected in circuit with a telephone transmitter 102 and with an amplifier triode 103 through a transformer 104. The output circuit of the amplifier triode 103 is also connected to the grid of the modulator triode 94.

At the receiving station, an antenna 110 is connected through a transformer 111 to a detector triode 112. The output circuit of the modulator triode 154 the detector triode 112 is connected through a transformer 113 to an oscillograph element 114. The oscillograph element may be similar to the oscillograph 89, previously described. The oscillograph element 114 is adapted to scan a lens 115 which is provided with a light transmitting section 116 that is divided into a series of parts. The number and relative position of these parts in the lens 115 are the exact duplicate of the light transmitting parts in the section 93 of the lens 90 at the transmitting station.

The rays of light from the light transmitting parts of the section 116 are adapted to fall upon a photoelectric cell 117. The photoelectric cell 117 is connected in circuit with an amplifier triode 118. cell 117 is also connected through a transformer 119 to the antenna 110. The output circuit of the amplifier 118 is inductively associated with a detector triodc 120 through a transformer 121. The output circuit of the detector triode 120 is connected to a pair of head phones, or other receiving device.

The photoelectric cell 117 is so positioned with res ect to the oscillograph 114 that, as the oscillhgraph moves on its axis, the light from the various parts of the lens 115 will always fall upon the photoelectric cell 117. This may be accomplished 'by having the light transmitting part 116 of the'lens 115 so arranged-that movement of the oscillo- The photoelectric graph, so as to reflectlight from another part, is equal to the angle between the photoelectric cell and the oscillograph mirror.

In Fig. 9, an oscillatory circuit, including the antenna 150, is connected through a tuning coil 151 to the plate circuit of the amplifier triode 152. The grid circuit of the amplifier triode 152 is connected through a transformer 153 to the plate circuit of the modulator triode 154. The grid circuit of is connected through a transformer 155 to a circuit adapted to generate a high-frequency oscillating current and which includes an oscillator triode 156. The grid circuit of the modulator triode 154 is also connected through a transformer 157 to an alternatingcurrent generator 158 of adefinite frequency.

An oscillograph element 159 is connected in circuit with the generator 158. The oscillograph element 159 is turned uponits axis under the influence of alternating current that is adapted to scan the face of the lens 160. The lens 160 contains a number of light transmitting sections 161 and a number of opaque sections 162.

Whenever a ray of light from one of the light transmitting sections falls upon the oscillograph element 159, it is reflected to the photoelectric cell 163. The photoelectric cell 163 is connected in circuit with a triode 164 which operates as a relay. The plate circuit of the triode 164 is connected through a transformer 165 to an amplifier triode 166. The plate circuit of the triode 164 is also connected through a' transformer 167 to an amplifier triode 168. The grid circuit of the amplifier triode 166 is connected through a transformer 169 to a telephone microphone 17 The grid circuit of the amplifier triode 166 is also connected through a transformer 171 to a variable frequency generator 172.

The grid circuit of the amplifier triode 166 contains a C battery so connected in the circuit as to place a negative potential upon its grid. The grid circuit. of the'amplifier triode 165. contains a C battery 174 so arranged as to place a positive potential upon its grid. The purpose of this arrangement will appear more fully hereinafter.

The plate circuit of the amplifier triode 166 is connected through a transformer 17.) to modulator triodes .176 and 177. The plate circuit of the amplifier triode. 168 is connected through a transformer 178 to the modulator triodes 176 and 177. The oscil lating circuit including the triode 178 is connected through a transformer 179 in cireuit with the modulator triodcs 176 and 177.

The output circuits of the modulator triodes 176 and 177 are connected through a transformer 180 to an amplifier triode 181. The output circuit of the amplifier triode 181 is connected through a' tuning c0il 182 to the oscillating, circuit ipcluding the antenna 150. The oscillating circuit, includ-v ing the antenna 150, is connected through a tuning coil 183 to an oscillating circuit 184. The circuit 184 is connected through transformers 185 and 186 to the grid circuit of the 'triode 164. The plate circuit of the triode 164 is connected through a transformer 187 to a detector triode 188. The output circuitof the detector triode 188 is connectcc through a transformer 189 to anamplifier triode 190. The output circuit of the amplifier triode 190 is connected to a telephone receiving device 191.

Having briefly described the apparatus shown in the-drawings, I Will now explain its detailed operation. For this purpose, it will be assumed that the circuit,'including the oscillator 7, is generating an oscillating current of a certain frequency, 800,000 cycles for example. The high-frequency *alternating current from this oscillating circuit is amplified by the operation of the triodes 5 and 3 and radiated by the antenna 1. by operating frequency current from generator 20, and also by microphonic current from the microphone 16 and masking frequency current from the generator 29, re spectivelyl The cathode electron streams are emitted from the cathodes 12 and 22 of the cathode-ray tubes 11 and 12, respectively.

As the coils 30v to 33, inclusive, are all (3011- This carrier current is modulated first nected in series in circuit with the genera tor 20, an alternating current traverses these coils and a magnetic field is set up in the path of the cathode ray stream at both the cathode'ray tubes 11,- and 21.. 13y this magnetic lield, the cathode ray is deflected at right angles thereto and swings in a plane perpendicular to the magnetic field. Inasmuch as the plate 10 of the cathode-ray tube 11 is connected through the secondary winding of the transformer 9 to the grid of the amplifier triode. 8 and the filament. of the cathode-ray tube 11 isconnected to the filament of the amplifier triode 8, when the cathode beam strikes any particular portion of the plate, there Will be a circuit closed and the current How in this circuit will be altered by any audible indication reaching the transmitter 16.that is connected to the primary of the transfo'imer 9.

7 Consequently, at that particular time, the.

high-frequency current generated by the oscillating triode7 will be modulated in accordance with the audible indication from the transmitter 16. When the cathode beam inthe cathodemay tube 11 passes through an opening in the metal plate 10, there will he no circuit ;.and, consequently, no signal modulation of the high-frequency carrier current. As the movement of the, beam takes place relatively fast, the interruptions in this circuit occur at such a rate that they may be neglected when received, inasmuch as the interruptions occur at a frequency above 40,000 cycles, this frequency beingdetermined by the frequency of the alternating current generated by the generator 20 and the number of openings in the plate 10.

The filament of the cathode-ray tube 31 is also connected to the filament of the triodc 8. While the plate 26 is connected to the grid of the said triode. The variable tllltliO-fl0- quency current generator 29, which generates the masking frequency current, thus operates to modulate the carriercnrrc'nt at the particular portions when the cathode beam strikes the metal plate 26. This modulation of the carrier current by the gcnerator 29 occurs every time that the cathode beam of the'eathode-ray tube 11 is passing, through an opening in the metal plate 10. Thus, the carrier t'requency current is modulated alternately by the signalling frequency current and the masking trequency; 7

At the receiving station, the high-fro quen cy current generated by the generator 20 is received by the antenna 40 and transferred through the transfer-mea to the amplifier 44. As the plate circuit of the amplifier triode 44- is connected to the coils 4-5 and 46 in the cathode-ray tube 47, an electromagnetic field is set up, which varies in the same manner as does the magnetic fields in the coils 30 to at the transmitting station. Thus, the cathode-ray beam of the 5a,. where, by the action of this detector the signalling frequency current will cause an audible indication in the head phones or receiving device.

During the time that the cathode-ray beam of the cathode-ray tube 21 is in contact with the metal plate 26, the cathode-ray beam in the tube 47 will be passing through an opening inv the metal plate 51 and, there-- fore, there will be no circuit for transferring the high-frequency current modulated by the masking frequency current to the detector 5 1, and this will be inaudible in the receiving device on account of the high-frequency current which is used for deflecting the oathode beams. The interruptions in the signalling current modulations occur with such speed that there is no audible interruption in the receiving device, the speed at which the signalling frequency current is interrupted being at a frequency above audibility.

It is, of course, obvious that, in place of i using a metal plate in cathode-ray tubes cut in the manner of the plates 10 and 26, irregularly cut plates may be used, such as those shown in Fig. 6. In this event, it would be necessary to usetwo operating or synchronizing frequency currents. The coils creating the magnetic fields in the cathoderay tubes would be placed at right angles to the coils shown. Thus, the cathode ray under the influence of the two operating frequency currents would cover the whole area [ill of the plates. On the other hand, it may be deemed desirable to provide a large number of metal plates cut with different patterns at both the transmitting and receiving station-s. When this is true, a master numbering plate can be provided, such as that shown in Fig. 5, which'is divided into a large number of divisions. Thus, by any ordinary means, the operators at the various stations can be apprised what particular plate is going to be used for transmitting by designating the plate to be used with reference to the coding plate. Of course, in

' the event that interchangeable plates are provided at the receiving stations, the oathode-ray tube will be constructed so that the modification of the transmitting station will now be described. The only difference between the operation of the system shown in this figure and that shown in Fig. 1 is that but one cathode-ray tube is used, this tube having both plates 67 and 68 similar to plates 10 and 26 mountedtherein. The circuit connections are otherwise the same.

The operation of the system in this case is identically the same as before, with the exception that one cathode-ray beam furnishes the conducting path for modulating the carrier frequency current with both the signalling frequency current and the variable masking frequency current.

Referring now to Fig. 8, the operation in this case is somewhat different from that before described, inasmuch as ordinary mechanical oscillographs are used at the transmitting and recelving stations in place of cathode-ray oscillographs. 4 By reason of the operation of the oscillat-r mg circuit including the triode 86, carrier frequency current is radiated by the antenna 80 and, at the same time, the antenna 80 I 87 also traverses the oscillograph element 89 andcauses it to swing on its axis from- J side to side.

Considering one position of the oscillograph element 89, when the light ray from one of' the transmitting parts of thesection 93 falls on the mirror of the oscillograph element, it is reflected on the photoelectric cell 92 This light ray from the line transmit-ting section causes current to flow in the circuit including the transmitter 102. The amplitude of this current is varied in accordance with any audible signals caused by the operation of the transmitter 102. This change in amplitude of the current flowing in the circuit is transferred to the amplifier triode 103 through the transformer 104. By

the operation of the amplifier 103, this current is amplified and transferred to the circuit including the triode 94. This current modulates the carrier current generated by the oscillator 97 in accordance With the signal given. This modulated carrier current is then amplified by the operation of the amplifier 100 and radiated by means of the antenna 80.

As the oscillograph element 89 moves, it will reflect a light ray from the light trans mitting section 93 on the photoelectric cell 91, and there will be no light ray reflected on the photoelectric cell 92. Consequently, the signalling circuit will be interrupted, inasmuch as the resistance of the photoelectric cell 92 becomes very high. The light ray ieflected on the photoelectric cell 91 causes the current of variable audio frequency of the generator 96 to transfer this current through the transformer 92 to the amplifier triode 93'. By the action of the amplifier triode 93, this current is amplified and transferred to the circuit including the tri ode 94, whereby this varying masking frequency current modulates the carrier current generated by the generator 97 and is transmitted after being amplified by the operation of the amplifier 95 by the antenna 80.

As the oscillograph element 89 swings from side to side, the signalling frequency current and the masking frequency current will be transmitted alternately. The speed at which the signalling frequency current is interrupted by the masking frequency current is determined by the frequency of the alternating current generated by the generator 87 which will be substantially 25,000 cycles per second. Thus, the voice current is interrupted several times for each alternation in the frequency of the current generated by the generator 87, by reason of the various light transmitting parts in the sections 93 and 94.

At the receiving station, the carrier current which is modulated in accordance with the alterations in the current from the alternator 87 is transferred through the transformer 111 to the detector 112, whereupon this current is demodulated and the current of the resultant frequency is transferred to the oscillograph element 114. As this current is of the same frequency as that generated by the generator 87 at the transmitting station, the oscillograph 114 will operate in synchronism with the oscillograph element 89 at the transmitting station.

As the oscillograph element swings back and forth, it will alternately engage the light and opaque parts in the section 116. Upon scanning a light transmitting part, the oscillograph element 89 at the transmitting station will be in the same relative position and, consequently, there will be a circuit closed at the transmitting station for modu-' lating the high-frequency carrier current with the signalling current. At the same time, at the receiving station, the photoelectric cell 117 will become conductive and a circuit will be closed for transmitting this modulated high-frequency current from the antenna 110 through the amplifier 118't0 the detector 120. By the action of the detector 120, the carrier frequency current is eliminated and the signalling or speech frequency current causes an audible indication in the telephone receivers, or other receiving device.

During the time that the photoelectric cell 91 at the transmitting station is active, the oscillograph 114 will be engaging an opaque portion of the section 115, and, consequently, the photoelectric cell 117 acts substantially the same as an insulator and there will be no circuit closed for the detector 120.

If any other receiving station attempts to listen in on this signalling without being provided with a lens patterned similar to the lens 115, the received indications will be unintelligible, by reason of the fact that the speech frequency current will alternate at a high rate of speed with the variable masking frequency current.

In the same manner as before described, the patterns of the lenses 90 and 115 may be changed, as desired, so as to render the interruptions in the speech frequency more or less complex.

Referring now to Fig. 9, the operation of this system is somewhat similar to that previously described. The circuit including the oscillator 156 is generating an oscillat ing current at a certain frequency, and this current is modulated by the triode at the frequency of the alternating-current generator 158. This modulated carrier current is then amplified by means of triode 152 and radiated by the antenna 150.

The oscillograph element 159 is also operated upon its axis at a frequency which depends upon the frequency of current from the generator 158. This frequency is sullici'ently high that, when multiplied by the number of opaque parts in the lens 160, the result is a frequency above audihilitlv, that is, above 20,000 cycles per second.

As the oscillograph element 159 swings to and fro, various impulses of light are reflected upon the photoelectric cell 163. Considering the oscillograph element 159 in a definite position so that a ray of light from one of the light transmitting parts, such as 162, falls upon the photoelectric cell 158. there will be a higher negative potential applied to the grid voltage and, consequentode to modulate through the modulator triodes 176 and 177 the carrier current generated by the oscillating circuit including the oscill r triode 15- 8. The modulated carrier .currcnt is amplified by means of the amplifier trioile 81 and radiated by means of the antenna 150. The grid of the triode 166 may be suitably biased by means of a C battery 173 to cause the trioile 166 to function suitably.

amplifying circuit. including the amplify-' ing triode 168, will now become effective and the carrier current generated by the 0s eillating current from the circuit including the oscillator 178 Will he modulated at the frequency of the variable frequency generafor 172 through the action of the modulator triodes 176 and 177.

The output of these modulators is amplified by means of the amplifier 181 and radiated by the antenna 150. In this manner, there is radiated from the antenna 150 a carrier current that is modulated at an operating or synchronizing frequency and a modulated carrier current that is intermittently modulated at a speech frequency and at a variable masking frequency.

lVhen a carrier current is received by the antenna 150 that is modulated intermittently at a marking frequency and at a signalling frequency, this modulated current will be transferred by means of the oscillating circuit 184: which is tuned to the particular frequency which it is desired to receive and to the grid of the triode 164. As the triode 164. operates under the control of the oscillographel ment 15.). the detector triode 188 ivill be effective only when'the photoelectric cell 163 is conductive. This occurs only at the time when the carrier current at the distant station is being modulated by the sig- .nalling frequency, and, consequently, only the vibration caused by the current or signalling frequency will be heard in the telehone receivim device 191. In thiscase, it

is assumed that the s \-'nclironizing frequency current is generated from the station shown in Fig. 9. which may be considered a central station.

Inasmuch as the current of signalling frequency is interrupted by the current of nuisking frequency at a frequency above audibility, the intcrruptioi'is in the signalling current will not be apparent in the telephone receiving device 191.

It Will be obvious that itis entirely possible to have the current of synchronizing fre-- quency generated at a central station, rather than at the transmitting station. In this event, the apparatus and circuits would diffor from those shown, only that at the transmitting station, in place of the generator 73, there Would be provided an amplifier triode connected to'coils, such as 74 and 7 5, Fig. 7 g The input circuit of this amplifier would be connected in inductive rel ation to the oscillatory circuit including the antenna 60 and would be resonant to current of the particular frequency that would be generated by the synchronizing frequency current generator at the central station. At the central station. there would be broadcasted a synchronizing frequency current.

It will be seen that this arrangement allows a number of transmitting stations to transmit even with only one station generating the synchronizing frequency current. There would be no interference in the signals from any of the transmitting stations, by reason of the fact that the currents of signalling and masking frequencies would be operated on different wave lengths.

My invention is not limited to the specific arrangement of the apparatus illustrated, but may be variously modified without departing from the spirit and scope thereof, as set forth inthe appended claims.

! claim as my invention:

1. In a system of intelligence communication. the combination with a transmitting station, means for generating a high-frequciu-y current thercat to create etherie disturbances. and a signalling device for controlling said high-frequency current, of a second device for controllii'ig said higl'i-frequency current. a source of alternating current, and means including a device having a space-current path for causing the controlling devices to become effective in turn in response to said alternating current.

2. In a signalling system, the con-ibination with a transmitting station. a source of high-frequency current for creating etheric disturbances, a receiving station for receiving said disturbances, and a signalling device at said transmitting station for controlling said high-frequency current. of a source of variable frequei'icy electric current at said station, means for periodically interrupting said cmitrolling operation and for simultaneously controlling said high frequency current by means of said variable frequency current, and means at said receiving station for receiving only the alternating-current frequency controlled by the current of signalling frequency.

3. In a signalling system, the combination with a transmitting station. a source of highfrequeucy current for creating etheric disturbances, a signalling device atsaid transmitting station for controlling said highfrequency current, of a source of variable frequency electric current at said station,

and means for periodically interrupting said controlling operation and for simultaneously controlling said current of high frequency by means of saidcurrent of variable frequency.

4. In a signalling system, the combination with a transmitting station, a source of high-frequency current for creating etheric disturbances, a receiving station for receiving said disturbances, and a signalling device at said transmitting station for controlling said high-frequency current, of a source of variable frequency electric current at said station, means for periodically.

interrupting said controlling operation and for simultaneously controlling said current of high frequency by means of said current of variable frequency, and means at said receiving station for eliminating from said receiving device the alternating current con trolled by said current of variable frequency.

5. In a signalling system, the combination with a transmitting station, means at said station for generating an electric current, means controlled by the current from said source for creating etheric disturbances, and a signalling device for controlling said current, of a second signalling device, asource of current of a predetermined frequency, and a thermionic device controlled by the current from said source for interrupting said controlling operation and for placing said first current under control of said second signalling device. f

6; In a signalling system, the combination with a transmitting station, means at said station for generating an electric current, means controlled by said current for creating etheric disturbances, and a signalling device for controlling said current, of a second signalling device, a source of current of a predetermined frequency, a thermionic device controlled by the current from said source for interrupting said controlling operation and for placing said first current under control of said second signalling device, a receiving device, means controlled by the current from said source for operating said device responsive to said first current when said first current is controlled by said first signalling device, and means for preventing the operation of said receiving device when said first current is controlled by said second signalling current.

7. In a signalling system, the combination ivith a transmitting station, a source of electric current at said transmitting station for creating etheric disturbinices, a receiving station. and means at said receiving station for receiving said disturbances, of a signalling device atsaid transmitting'station for controlling said current, a second signalling device at said transmitting station, thermionically controlled, synchronously operating devices at said transmitting and receiving stations, and means controlled by the device at the transmitting station for intermittently interrupting the control of said current by the first signalling device and for causing said second signalling device to control said current.

8. In a signalling system, the combination -with a transmitting station, a source of electric current at said transmitting station for creating etheric disturbances, a receiving station, and means at said receiving station for transmitting station for intermittently interriipting the control of said current by the rst signalling device and for causing said second signalling device to control said current, and means controlled by the device at the receiving station for preventing the operation of said receiving means during the control of said current by said second signalling device.

9. In a signalling system, the combination with atransmitting station, a source of electric current at said transmitting station for creating etheric disturbances, a receiving station, and means at said receiving station for receiving said disturbances, of a signalling device at said transmitting station for controlling said current, asecond signalling device at said transmitting station, thermionically controlled, synchronously operating devices at said transmitting and receiving stations, means controlled by the device at the transmitting station for intermittently interrupting the control of said current by the'first signalling'device and "for causing said second signalling device to control said current, and means controlled by the device at said receiving station for preventing the operation of said receiving means, except when said current is controlled by said first signalling device.

'10. In a signalling system, the combina tion with a transmitting station, a source of electriccurrent thereat for creating etheric disturbances inthe receiving station. and means at said receiving station for receiving said disturbances, a signalling device at said transmitting station for controlling said current, a: second signalling device at said transmitting station, thermionically controlled, synchronously operating devices at said transmitting and receiving stations, means controlled by the synchronously operating device at the transmitting station for interrupting the control of said current b the first signalling device at a frequency a ove audibility', and means controlled by the synchronously operating device at the receiving station for preventing the operation of said receiving means, while said current is controlled by said second signalling device.

ll. ln a signalling system, the combination with a transmitting and a receiving station, oi' a device at the transmitting station and a device at the receiving station for generating an electron stream, means for deflecting the electron stream from its normal path at both the transmitting and receiving stations, a source of electric current at said transmitting station for creating.

etheric disturbances, means at said receiving station for detecting said etheric disturbances. a second source of electric current at said transmitting station for deflecting said electron streams, a signalling device at said transmitting station for controlling sa'id first electric current, a second signalling device, means controlled by the electron stream at said transmitting station for rendering said second signalling device eflective to control the first electric current, and means controlled by the electron stream at said receiving station for preventing the operation of said receiving means, except When the first electric current is controlled by said first signalling device.

12. In. a signalling system, the combinationwith a transmitting and a receiving-station, of a device at the transmitting station and a device at the receiving station for generating an electron strea'm, means for deflecting the electron stream from its normal path atboth the transmitting and receiving stations, a source of electric current at said transmitting station for creating etheric disturbances, means atsaid receiving station for detecting said etheric disturbances, a second source of electric current at said transmitting station for deflecting said electron stream, a signalling device -at said transmitting station for controlling the first electric current, a second signalling device, means controlled by the electron stream at said transmitting station for rendering said second signalling device efiective to control said first electric current, and means controlled by the electron stream at said receiving station for controlling the operation of said receiving means. 13. In a signalling system, the combination with a transmitting and a receiving station, of a device at the transmitting station and a device at the receiving station for generating an electron stream, means for deflecting the electron stream from its normal path at both the transmitting and receiving stations, a source of electric current at said' transmitting station for creating etheric disturbances, means at said receiving station for detecting said etheric disturbances, a second source ofeleetric current at said transmitting station for deflect ing said electron streams in synchronism, a

signalling device atsaid transmitting station for controlling the first electric current, a second signalling device, means controlled by the electron stream at said trans mitting station forv rendering said second signalling device eli'ective to control the first electric current, and means controlled by the electron stream at said receiving station for preventing the operation of said receiving means, except when said first electric current controlled by said first signalling device.

14. The combination with a transmitting station, of a device at the transmitting station for generating an electron stream, means for deflecting the electron stream from its normal path at the station, a source of electric current at said transmitting station for creating 'etheric disturbances, a second source of electric current at said transmitting station for deflecting said elecv tron stream, a signalling device at said station for controlling the first electric current, a signalling device at said transmitting station for controlling said first electric current, and means controlled by said electron stream for interrupting the controlling action of said signalling device.

15. The combination with a transmitting station, of a device at the transmitting sta tion for generating an electron stream, means for deflecting the electron stream from its-normal path at the station, a source of electric current at said station for creating etherie disturbances, a second source of electric current at said station for deflecting said electron stream, a signalling device at said station for controlling said first electric current, a second signalling device, and means controlled by said electron stream for interrupting the controlling operation of for controlling said first electric current, a

second signalling device, and means controlled by said electron stream for enablin said second signalling device to control sai electric current.

17. In a signalling system, the combina tion. with a transmitting and a receiving station, a source of electric current at said transmitting station'for creating etheric disturbanc s. means at. said receiving station for receiving said disturbances, an interrupting device at said transmitting station,

an interrupting device at said receiving station, means located at a point separate from tion, asource of electric current at said transmitting station for creating etheric disturbances, means at. said receiving station for Y receiving said disturbances, an interrupting device at said transmitting station, an interrupting device at said receiving station, means located at a point separate from said transmitting or receiving station for causing said interrupting devices to operate in synchronism, a signalling device at said transmitting station for controlling said electric current, a second signalling device, means controlled by the interrupting device at the transmitting station for stopping the controlling operation of said first signalling device and for placing said electric current under the control of said second signalling device, and means controlled by the intcrrupting device at the receiving station for preventing the operation of said receiving signalling device. a

electric current at said transmitting station for creating etheric disturbances, an interrupting device at said transmitting station, means located at a point separate from said transmitting station for causing said inter rupting device to operate, a signalling device at said transmitting station for controlling said electric current, and means controlled by said interrupting device for preventing the control of'said electric current by said 20. In a signalling system, the combination with a transmitting statlon, a source of electric current at sald transmitting station :forcreating etheric disturbances, an interrupting device at said transmitting station.

means located at a point separate from said transmitting station for causing said interrupting device to operate, a signalling device at said transmitting station for controlling said electric current, a second signalling device, and means controlledby said interrupt-'- ing device for intermittently stopping the controlling operation of said first signalling device and for placing said elcctriccurrcnt under the control of said second signalling device.

In testimony whereof, I have hereunto sgbscribed my name this 13th day of March, 1 24.

VLAlDIMIR K. ZWORYKIN. 

